Expression in Yeast of the Metacaspase Scp3 from the Fungus Schizophyllum commune

Metacaspases are caspase homologs that are found in plants, fungi, and protists. They are involved in programmed cell death, a structured and regulated process to break down cells. There is limited information available on metacaspases and further research is necessary to understand how they work. One reason metacaspases are studied is that they are considered to be a potential drug target for pathogenic microorganisms. Five metacaspases scp1-5 were identified in S. commune through their similarity to the yeast metacaspase Yca1. The overall goal of the lab is to study and characterize these proteins. This thesis outlines the path taken to express the Schizophyllum commune metacaspase scp3 in yeast. Previous efforts in our lab to express metacaspases in E. coli have not been successful. I hypothesized that yeast would be a more desirable expression vehicle due to its closer relationship to S. commune; a more similar environment could yield more active protein. Scp3 has been successfully cloned into a yeast expression vector pYES2.1/V5-His-TOPO® and β-galactosidase expression has been obtained in yeast with the expression control vector pYES1.2/V5-His/lacZ. Future work on this project will be to perform a point mutation in the expression plasmid to remove a stop codon before the scp3 sequence

Generalize or personalize:do dogs transfer an acquired rule to novel situations and persons?

Recent studies have raised the question of whether dogs, like human infants, comprehend an established rule as generalizable, normative knowledge or rather as episodic information, existing only in the immediate situation. In the current study we tested whether dogs disobeyed a prohibition to take a treat (i) in the presence of the communicator of the ban, (ii) after a temporary absence of the communicator, and (iii) in the presence of a novel person. Dogs disobeyed the rule significantly more often when the communicator left the room for a moment or when they were faced with a new person, than when she stayed present in the room. These results indicate that dogs "forget" a rule as soon as the immediate human context becomes disrupted

HSV-1 glycoprotein endocytosis

Herpes simplex virus-1 (HSV-1) is a large enveloped DNA virus that belongs to the family of Herpesviridae. It has been recently shown that the cytoplasmic membranes that wrap the newly assembled capsids are endocytic compartments derived from the plasma membrane. Here, we show that dynamin-dependent endocytosis plays a major role in this process. Dominant-negative dynamin and clathrin adaptor AP180 significantly decrease virus production. Moreover, inhibitors targeting dynamin and clathrin lead to a decreased transport of glycoproteins to cytoplasmic capsids, confirming that glycoproteins are delivered to assembly sites via endocytosis. We also show that certain combinations of glycoproteins colocalize with each other and with the components of clathrin-dependent and -independent endocytosis pathways. Importantly, we demonstrate that the uptake of neutralizing antibodies that bind to glycoproteins when they become exposed on the cell surface during virus particle assembly leads to the production of non-infectious HSV-1. Our results demonstrate that transport of viral glycoproteins to the plasma membrane prior to endocytosis is the major route by which these proteins are localized to the cytoplasmic virus assembly compartments. This highlights the importance of endocytosis as a major protein-sorting event during HSV-1 envelopment.This work was supported by grants from the Leverhulme Trust (grant RPG‐2012‐793), the Royal Society (University Research Fellowship UF090010), the Engineering and Physical Sciences Research Council, UK (grant EP/H018301/1, EP/L015889/1) and by the Medical Research Council (grant MR/K015850/1)

Injection-dependent Minority Carrier Lifetime in Epitaxial Silicon Layers by Time-resolved Photoluminescence

AbstractTime-resolved photoluminescence (TRPL) is used to evaluate the injection-dependent effective minority carrier lifetime of high resistivity epitaxial silicon layers grown on highly doped CZ-Si substrates. Effective lifetimes ranging from 10μs to 200μs are estimated for excess carrier densities between 1x1017 cm-3 and 2x1016 cm-3. Standard models are used to separate the contribution from the different recombination mechanisms. The influence of the epitaxial layer and substrate parameters on the minority carrier effective lifetime measurement is discussed

Numerical Simulation of Vertical Silicon Nanowires based Heterojunction Solar Cells

Abstract Nanowires (NWs) solar cells are expected to outperform the thin-film counterparts in terms of optical absorptance. In this theoretical study we optimize the geometry of vertical crystalline-amorphous silicon core-shell NW arrays on doped ZnO:Al (AZO)-Glass substrate by means of 3-D optical simulations in order to maximize the photon absorption. The optimized geometry is investigated by means of 3-D TCAD numerical simulation in order to calculate the ultimate efficiency and the main figures of merit by taking into account recombination losses. We show that optimized 10 μm-long crystalline – amorphous silicon core-shell (c-Si/a-Si/AZO/Glass) NWs can reach photo-generated current up to 22.94 mA/cm 2 (above 45% larger than that of the planar counterpart with the same amount of absorbing material) and conversion efficiency of 13.95%

Modélisation du comportement de composite à matrice céramique sous sollicitation de fatigue

International audienceLe présent article propose une approche permettant de déterminer la durée de vie d'un composite à matrice céramique en fatigue. Cette approche est mise en place par un couplage entre un modèle d'endommagement purement mécanique et un modèle basé sur la physico-chimie du matériau. En effet, la physico-chimie du matériau joue un rôle très important sur la tenue à long terme du composite. Sous atmosphère oxydante, les composites à matrice céramique s'oxydent, ce qui entraîne une rupture prématurée du matériau. Cependant la création d'une matrice multiséquencée autocicatrisante permet, à partir d'une certaine température, la formation d'un bouchon de verre, limitant l'oxydation du composite. Le modèle mécanique permet de calculer la loi de comportement en statique, puis en fatigue par un accroissement de l'endommagement matriciel directement lié au cyclage. On constate que le cyclage influence l'endommagement du composite et donc l'oxydation du matériau. Le modèle physico-chimique permet, quant à lui, de prendre en compte les cinétiques d'endommagement des fibres liées à l'oxydation de l'interphase, mais aussi la création du bouchon de verre limitant cette oxydation. L'oxydation de l'interphase va fortement dépendre du temps d'ouverture des fissures. Le modèle physico-chimique est donc fonction du temps alors que le modèle mécanique dépend directement du nombre de cycles, avec de plus la nécessité de coupler ces deux modèles

Modélisation de solides à nanocristaux de silicium

Les propriétés physico-chimiques d'un nanocristal semi-conducteur sphérique, intermédiaires entre la molécule et le solide, dépendent de sa taille. Empilés ou dispersés, ces nanocristaux sont les briques architecturales de nouveaux matériaux fonctionnels aux propriétés ajustables, en particulier pour l optoélectronique. Cette thèse s'inscrit dans le développement de ces nouveaux matériaux et présente avant tout une méthodologie pour la simulation du transport électronique dans un solide à nanocristaux en régime de faible couplage électronique appliquée à des nanocristaux de silicium dans une matrice de SiO2 pour les applications photovoltaïques. La cinétique du déplacement des porteurs est liée au taux de transfert tunnel (hopping) entre nanocristaux. Ces taux sont calculés dans le cadre de la théorie de Marcus et prennent en compte l'interaction électron-phonon dont l'effet du champ de polarisation dans la matrice ainsi que les interactions électrostatiques à courte et longue portée. Le calcul des états électroniques (électrons et trous) en théorie k.p associé à l'utilisation de la formule de Bardeen donne au code la capacité, par rapport à la littérature, de fournir des résultats (mobilité ou courant) en valeur absolue. Les résultats de mobilité ainsi obtenus pour des empilements cubiques idéaux viennent contredire les résultats de la littérature et incitent à considérer d'autres matériaux notamment en ce qui concerne la matrice pour obtenir de meilleurs performances. En outre, les résultats de simulation de dispositifs montrent l'impact considérable des électrodes sur les caractéristiques courant-tension. Aussi, un nouvel algorithme Monte-Carlo Cinétique accéléré a été adapté afin de pouvoir reproduire le désordre inhérent à la méthode de fabrication tout en maintenant un temps de simulation raisonnable. Ainsi l'impact du désordre en taille se révèle faible à température ambiante tandis que les chemins de percolation occultent la contribution des autres chemins de conduction. Des résultats de caractérisation comparés aux simulations tendent par ailleurs à indiquer que ces chemins peuvent concentrer les porteurs et exhiber un phénomène de blocage de coulomb. Enfin, la section efficace d'absorption est calculée théoriquement et permet d'obtenir le taux de génération sous illumination qui se révèle proche du silicium massif. Et une méthode en microscopie à sonde de Kelvin est décrite pour caractériser la durée de vie des porteurs c'est-à-dire le taux de recombinaison, les résultats ainsi obtenus étant cohérents avec d'autres techniques expérimentales.The physicochemical properties of a spherical semiconductor nanocrystal, intermediate between the molecule and the solid depend on its size. Stacked or dispersed, these nanocrystals are building blocks of new functional materials with tunable properties, particularly appealing for optoelectronics. This thesis takes part in the development of these new materials. It mainly presents a methodology for the simulation of electronic transport in nanocrystal solids within the weak electronic coupling regime. It is applied to a material made of silicon nanocrystals embedded in silicon oxide and considered for photovoltaïc applications. The displacement kinetics of charge carriers is related to the tunneling transfer rate (hopping) between nanocrystals. These rates are calculated within the framework of Marcus theory and take into account the electron-phonon interactions, the effect of the bias field and the electron-electron interactions at short and long range. The calculation of electronic states (electrons and holes) in k.p theory associated with the use of Bardeen's formula provides, compared to previous works, results (mobility or current) in absolute terms. The mobility thus computed is far lower than the results of the literature and encourage to consider other materials. Furthermore, the device simulations show the significant impact of the electrodes on the current-voltage characteristics. Also, a new accelerated kinetic Monte-Carlo algorithm has been adapted in order to reproduce the disorder inherent in the manufacturing process while maintaining a reasonable simulation time. Thus the impact of the size disorder is poor at room temperature while the percolation paths shunt the contribution of other conduction paths. Characterization results compared to simulations tend to show that these paths concentrate carriers and exhibit Coulomb blockade phenomenon. Finally, the absorption cross section is calculated theoretically to obtain the generation rate under illumination. It is similar to the bulk silicon one. And a method employing a Kelvin probe microscope is described to characterize the carrier lifetime, namely the recombination rate. The results thus obtained are consistent with other experimental technics.VILLEURBANNE-DOC'INSA-Bib. elec. (692669901) / SudocSudocFranceF